diff options
| author | Ard Biesheuvel <ardb@kernel.org> | 2022-02-03 09:22:01 +0100 |
|---|---|---|
| committer | Sudeep Holla <sudeep.holla@arm.com> | 2022-02-08 23:06:40 +0000 |
| commit | cdf157faaafe36c0823148587a78147200898e87 (patch) | |
| tree | 09c8ef73589c35543066a858a5115d62852ecc52 /drivers/firmware | |
| parent | b1a1b152321107c74e1bfeaa729582174405ab23 (diff) | |
| download | lwn-cdf157faaafe36c0823148587a78147200898e87.tar.gz lwn-cdf157faaafe36c0823148587a78147200898e87.zip | |
firmware: arm_scmi: Disable ftrace for Clang Thumb2 builds
The SMC calling convention designates R0-R7 as input registers in
AArch32 mode, and this conflicts with the compiler's use of R7 as a
frame pointer when building in Thumb2 mode. Generally, we don't enable
the frame pointer, and GCC happily enables the -pg profiling hooks
without them. However, Clang refuses, and errors out with the message
below:
drivers/firmware/arm_scmi/smc.c:152:2: error: write to reserved register 'R7'
arm_smccc_1_1_invoke(scmi_info->func_id, 0, 0, 0, 0, 0, 0, 0, &res);
^
include/linux/arm-smccc.h:550:4: note: expanded from macro 'arm_smccc_1_1_invoke'
arm_smccc_1_1_smc(__VA_ARGS__); \
^
Let's just disable ftrace for the compilation unit when building this
configuration.
Link: https://lore.kernel.org/r/20220203082204.1176734-11-ardb@kernel.org
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>
Diffstat (limited to 'drivers/firmware')
| -rw-r--r-- | drivers/firmware/arm_scmi/Makefile | 7 |
1 files changed, 7 insertions, 0 deletions
diff --git a/drivers/firmware/arm_scmi/Makefile b/drivers/firmware/arm_scmi/Makefile index ef66ec8ca917..8d4afadda38c 100644 --- a/drivers/firmware/arm_scmi/Makefile +++ b/drivers/firmware/arm_scmi/Makefile @@ -12,3 +12,10 @@ scmi-module-objs := $(scmi-bus-y) $(scmi-driver-y) $(scmi-protocols-y) \ $(scmi-transport-y) obj-$(CONFIG_ARM_SCMI_PROTOCOL) += scmi-module.o obj-$(CONFIG_ARM_SCMI_POWER_DOMAIN) += scmi_pm_domain.o + +ifeq ($(CONFIG_THUMB2_KERNEL)$(CONFIG_CC_IS_CLANG),yy) +# The use of R7 in the SMCCC conflicts with the compiler's use of R7 as a frame +# pointer in Thumb2 mode, which is forcibly enabled by Clang when profiling +# hooks are inserted via the -pg switch. +CFLAGS_REMOVE_smc.o += $(CC_FLAGS_FTRACE) +endif |